diff --git a/components/script/dom/domtokenlist.rs b/components/script/dom/domtokenlist.rs
index f74887d0899..3968b2084cb 100644
--- a/components/script/dom/domtokenlist.rs
+++ b/components/script/dom/domtokenlist.rs
@@ -139,6 +139,32 @@ impl DOMTokenListMethods for DOMTokenList {
         self.element.set_tokenlist_attribute(&self.local_name, value);
     }
 
+    // https://dom.spec.whatwg.org/#dom-domtokenlist-replace
+    fn Replace(&self, token: DOMString, new_token: DOMString) -> ErrorResult {
+        if token.is_empty() || new_token.is_empty() {
+            // Step 1.
+            return Err(Error::Syntax);
+        }
+        if token.contains(HTML_SPACE_CHARACTERS) || new_token.contains(HTML_SPACE_CHARACTERS) {
+            // Step 2.
+            return Err(Error::InvalidCharacter);
+        }
+        // Steps 3-4.
+        let token = Atom::from(token);
+        let new_token = Atom::from(new_token);
+        let mut atoms = self.element.get_tokenlist_attribute(&self.local_name);
+        if let Some(pos) = atoms.iter().position(|atom| *atom == token) {
+            if !atoms.contains(&new_token) {
+                atoms[pos] = new_token;
+            } else {
+                atoms.remove(pos);
+            }
+        }
+        // Step 5.
+        self.element.set_atomic_tokenlist_attribute(&self.local_name, atoms);
+        Ok(())
+    }
+
     // https://dom.spec.whatwg.org/#concept-dtl-serialize
     fn Stringifier(&self) -> DOMString {
         self.element.get_string_attribute(&self.local_name)
diff --git a/components/script/dom/webidls/DOMTokenList.webidl b/components/script/dom/webidls/DOMTokenList.webidl
index c9125285f74..21be3590c0a 100644
--- a/components/script/dom/webidls/DOMTokenList.webidl
+++ b/components/script/dom/webidls/DOMTokenList.webidl
@@ -18,6 +18,8 @@ interface DOMTokenList {
   void remove(DOMString... tokens);
   [Throws]
   boolean toggle(DOMString token, optional boolean force);
+  [Throws]
+  void replace(DOMString token, DOMString newToken);
 
   [Pure]
            attribute DOMString value;
diff --git a/tests/wpt/metadata/dom/interfaces.html.ini b/tests/wpt/metadata/dom/interfaces.html.ini
index d79c09e1674..0ebcd506c2a 100644
--- a/tests/wpt/metadata/dom/interfaces.html.ini
+++ b/tests/wpt/metadata/dom/interfaces.html.ini
@@ -156,18 +156,9 @@
   [DOMSettableTokenList interface object name]
     expected: FAIL
 
-  [DOMTokenList interface: operation replace(DOMString,DOMString)]
-    expected: FAIL
-
   [DOMTokenList interface: operation supports(DOMString)]
     expected: FAIL
 
-  [DOMTokenList interface: document.body.classList must inherit property "replace" with the proper type (6)]
-    expected: FAIL
-
-  [DOMTokenList interface: calling replace(DOMString,DOMString) on document.body.classList with too few arguments must throw TypeError]
-    expected: FAIL
-
   [DOMTokenList interface: document.body.classList must inherit property "supports" with the proper type (7)]
     expected: FAIL
 
diff --git a/tests/wpt/web-platform-tests/dom/nodes/Element-classlist.html b/tests/wpt/web-platform-tests/dom/nodes/Element-classlist.html
index 9c0ff05efd9..cad3669da11 100644
--- a/tests/wpt/web-platform-tests/dom/nodes/Element-classlist.html
+++ b/tests/wpt/web-platform-tests/dom/nodes/Element-classlist.html
@@ -77,6 +77,13 @@ test(function () {
 test(function () {
   assert_throws( 'SYNTAX_ERR', function () { elem.classList.toggle(''); } );
 }, '.toggle(empty_string) must throw a SYNTAX_ERR');
+test(function () {
+  assert_throws( 'SYNTAX_ERR', function () { elem.classList.replace('', 'foo'); } );
+  assert_throws( 'SYNTAX_ERR', function () { elem.classList.replace('foo', ''); } );
+  assert_throws( 'SYNTAX_ERR', function () { elem.classList.replace('', 'foo bar'); } );
+  assert_throws( 'SYNTAX_ERR', function () { elem.classList.replace('foo bar', ''); } );
+  assert_throws( 'SYNTAX_ERR', function () { elem.classList.replace('', ''); } );
+}, '.replace with empty_string must throw a SYNTAX_ERR');
 test(function () {
   assert_throws( 'INVALID_CHARACTER_ERR', function () { elem.classList.contains('a b'); } );
 }, '.contains(string_with_spaces) must throw an INVALID_CHARACTER_ERR');
@@ -89,6 +96,20 @@ test(function () {
 test(function () {
   assert_throws( 'INVALID_CHARACTER_ERR', function () { elem.classList.toggle('a b'); } );
 }, '.toggle(string_with_spaces) must throw an INVALID_CHARACTER_ERR');
+test(function () {
+  assert_throws( 'INVALID_CHARACTER_ERR', function () { elem.classList.replace('z', 'a b'); } );
+  assert_throws( 'INVALID_CHARACTER_ERR', function () { elem.classList.replace('a b', 'z'); } );
+  assert_throws( 'INVALID_CHARACTER_ERR', function () { elem.classList.replace('a b', 'b c'); } );
+}, '.replace with string_with_spaces must throw a INVALID_CHARACTER_ERR');
+test(function () {
+  var foo = document.createElement('div');
+  foo.className = 'token1 token2 token3'
+  foo.classList.replace('token1', 'token3');
+  assert_equals( foo.classList.length, 2 );
+  assert_false( foo.classList.contains('token1') );
+  assert_true( foo.classList.contains('token2') );
+  assert_true( foo.classList.contains('token3') );
+}, '.replace with an already existing token')
 elem.className = 'foo';
 test(function () {
   assert_equals( getComputedStyle(elem,null).fontStyle, 'italic', 'critical test; required by the testsuite' );
@@ -224,6 +245,58 @@ test(function () {
   assert_false( elem.classList.contains('foo') );
   assert_false( elem.classList.contains('FOO') );
 }, 'classList.toggle must be case-sensitive when removing tokens');
+test(function () {
+  secondelem.className = 'foo FOO'
+  secondelem.classList.replace('bar', 'baz');
+  assert_equals( secondelem.classList.length, 2 );
+  assert_equals( secondelem.classList + '', 'foo FOO', 'implicit' );
+  assert_equals( secondelem.classList.toString(), 'foo FOO', 'explicit' );
+}, 'classList.replace replaces arguments passed, if they are present.');
+test(function () {
+  secondelem.classList.replace('foo', 'bar');
+  assert_equals( secondelem.classList.length, 2 );
+  assert_equals( secondelem.classList + '', 'bar FOO', 'implicit' );
+  assert_equals( secondelem.classList.toString(), 'bar FOO', 'explicit' );
+  assert_false( secondelem.classList.contains('foo') );
+  assert_true( secondelem.classList.contains('bar') );
+  assert_true( secondelem.classList.contains('FOO') );
+}, 'classList.replace must replace existing tokens');
+test(function () {
+  assert_not_equals( getComputedStyle(secondelem,null).fontStyle, 'italic' );
+}, 'classList.replace must not break case-sensitive CSS selector matching');
+test(function () {
+  secondelem.className = 'token1 token2 token1'
+  secondelem.classList.replace('token1', 'token3');
+  assert_equals( secondelem.classList.length, 2 );
+  assert_false( secondelem.classList.contains('token1') );
+  assert_true( secondelem.classList.contains('token2') );
+  assert_true( secondelem.classList.contains('token3') );
+}, 'classList.replace must replace duplicated tokens');
+test(function () {
+  secondelem.className = 'token1  token2  token3';
+  secondelem.classList.replace('token2', 'token4');
+  assert_equals( secondelem.classList + '', 'token1 token4 token3', 'implicit' );
+  assert_equals( secondelem.classList.toString(), 'token1 token4 token3', 'explicit' );
+}, 'classList.replace must collapse whitespace around replaced tokens');
+test(function () {
+  secondelem.className = ' token1 token2  ';
+  secondelem.classList.replace('token2', 'token3');
+  assert_equals( secondelem.classList.length, 2 );
+  assert_equals( secondelem.classList + '', 'token1 token3', 'implicit' );
+  assert_equals( secondelem.classList.toString(), 'token1 token3', 'explicit' );
+}, 'classList.replace must collapse whitespaces around each token');
+test(function () {
+  secondelem.className = '  token1  token2  token1  ';
+  secondelem.classList.replace('token2', 'token3');
+  assert_equals( secondelem.classList + '', 'token1 token3', 'implicit' );
+  assert_equals( secondelem.classList.toString(), 'token1 token3', 'explicit' );
+}, 'classList.replace must collapse whitespaces around each token and remove duplicates');
+test(function () {
+  secondelem.className = '  token1  token2  token1  ';
+  secondelem.classList.replace('token1', 'token3');
+  assert_equals( secondelem.classList + '', 'token3 token2', 'implicit' );
+  assert_equals( secondelem.classList.toString(), 'token3 token2', 'explicit' );
+}, 'classList.replace must collapse whitespace when replacing duplicate tokens');
 test(function () {
   assert_not_equals( getComputedStyle(elem,null).fontStyle, 'italic' );
 }, 'CSS class selectors must stop matching when all classes have been removed');